While we here at Bright Agrotech are fortunate (or unfortunate?) enough to not have to worry about extreme growing temperatures for long periods of time, this is not the case for many of our Upstart Farmers. We know farmers growing in hoop houses, warehouses, and even basements all over the country. Some of them have to deal with temperatures over 100 °F for most of the summer!
Since most crops require cooler temperatures, greenhouse cooling is a very important topic. When it comes to cooling a greenhouse, there are several techniques. We've demonstrated one with our roll-up sidewall discussion, but today we're going to dive deeper into other means of cooling a greenhouse.
Best practices for cooling a greenhouse
Good ventilation = good air circulation.
And good air circulation means better temperature regulation and gas exchange. This is important any greenhouse, and is very easy to implement.
Most greenhouses are built with windows and fans already present. If not, then you might have to prop open a door and use your own fans. This doesn't have to be a fancy setup to work!
Using shade cloth
A heavy shade cloth or opaque structure over your fish tanks will do you two favors:
- First, it will minimize algae, which only need a small amount of light to photosynthesize.
- Second, it will help regulate the temperature of your fish tanks. I cannot overstate the importance of this. Your fish tanks hold the majority of the thermal mass in your system. This affects both your crops and your fish.
Evaporative is relatively cheap and is very effective in drier climates. Typically, this cooling method uses a cooling pad with fans. Water is pumped over the pads and evaporates into the air, cooling the surrounding area.
Cooling by fogging
Fogging is a method in which water is fogged or misted from the roof of the greenhouse onto your crops. Usually misting nozzles or sprinklers must be installed. This method can be practical in certain situations, but isn't our top recommendation. Excess moisture can encourage fungi and mists are short-lived. If you already have sprinklers or nozzles installed, however, this can be a great tool in emergency situations because it lowers the temperature quickly.
Evaporation and fogging will only work in dry climates. In more humid climates, air conditioning is one of the options available to you.
Low grade geothermal cooling
Low grade geothermal heating and cooling is a way of storing and dispensing thermal energy from the earth.
In warm weather, the air is circulated through underground pipes, where water vapor condenses and the air is cooled. It is recirculated back into the greenhouse, leaving heat and moisture behind.
Cooling with chillers
Chillers, which are typically used for aquariums, can be very effective in aquaponics. There are dozens of companies that sell chillers. Active Aqua sells 4 sizes of chillers, ranging from 960 to 10,370 BTU's.
Measuring cooling power
The "cooling power" of a product may be listed in two different ways:
A BTU calculator will tell you how much cooling power you will need. Some products list the BTU power they have in the description. Other products give the degrees of cooling that they are capable of. This is usually based on the assumption that your greenhouse is within a certain width.
For example: The product description of a certain cooling pad (see the photo on the right) may say that it is capable of lowering the greenhouse temperature by 10 to 20 degrees if the cooling pad extends along the whole sidewall.
However: the cooling effect of that pad will be lower for a greenhouse that is fifty feet wide than it is for a greenhouse that is ten feet wide. See what I mean?
Another factor that will influence the effectiveness of evaporative pads, fogging, etc. is humidity.
The drier the environment, the more effective these types of coolers will be.
Your options for keeping your greenhouse cool aren't nearly as limited as you might think. Like pest control, environment control requires a little creative thinking to piece together controls that work well for your specific situation.
Check out how Tracy Holz in Anna, Texas, cools his aquaponics greenhouse.